Update field of a collection based on another collection - MongoDB

Question

I have two collections The structure of collection A is

{
     id:
     product:
}

The structure of collection B is

{
     id:
     product:
     status:
}

I want to update collection B like if a product exists in collection A, then it will set status 1 to the corresponding document of collection B.

The SQL syntax would be like

UPDATE B SET B.STATUS = 1 WHERE B.PRODUCT IN (SELECT PRODUCT FROM A);

I just need to do the same in MongoDB. Thanks in advance.

Answer 1

In MongoDB 4.2 you can do this with aggregation.

• Aggregate collection A
• $lookup from collection B with local and foreign fields both set to "product"
• $unwind the array returned from lookup
• $replaceRoot to make the looked up document to root
• $project status: {$literal:1}
• $merge with collection B